Method of producing colored



Reisaued July 5, 1938 PATENT OFFICE 'ME'I HOD OF PRODUCING COLORED CONCRETE Fred H. Amon, Weston, Masa, assignor, by mesne assignments, to Dewey and Almy Chemical Company, Cambridge, Mass, a corporation of Massachusetts No Drawing. Original No. 1,910,419, dated May 23, 1933, SerialNo. 520,717, March 6, 1931. Application for reissue April 22, 1938, Serial No.

This invention relates to the art of producing colored concrete, and in theterm concrete is included all compositions of cement and materials of mixed ingredients which have the property of setting to produce a rigid structure.

My invention comprises an improved method of producing colored concrete, which is characterized by the use of powdered carbon black in the form of a liquid suspension. It includes also within its scope the improved colored concrete herein described as produced by the method oi.

my invention.

An important field of use of my invention is in the production of colored sections or stripes in concrete road surfaces, imitation marble for in-' terior finish, soda fountains, tiles, friezes, panels or the like. In the production of colored concrete, it has been the practice heretofore to employ carbon black in powdered or pasteform. However, in order to produce concrete having a color of satisfactory character and intensity, it has been necessary to include in its composition an amount of carbon black which has had a detrimental effect upon the strength of the resulting structure. For example, in order to produce a black concrete of acceptable color, it has been sometimes necessary to include as much as 10%,, dry weight, of the carbon black, with a resulting reduction of compressive strength in 30. the set concrete to below 70% of that of uncolored concrete otherwise of the same composition. The present invention deals with this problem and its object is the production of colored concrete of high compressive strength, satisfactory color and low pigment content.

For example, I have found it entirely practicable to produce with 3% content of dispersed carbon black a black concrete comparing favorably in color to that containing carbon black of commercial form, and in the structure so produced in accordance with my invention the reduction of strength resulting from the addition of the pigment does not exceed 3 or 4%.

For purposes of illustration, I will now describe 5. the practice of my improved method as applied 5 Claims. "(01. lot-24) A liquid suspension of the carbon black may be prepared by stirring or beating the carbonblack in water'containing a suitable dispersing agent in approximately the proportions of one pound of carbon black to two pounds of water, thus producing a smooth paste. In this way a very-definite and uniform separation or dispersion of the individual particles of carbon black is brought about and this is assisted by the addition of the colloidal dispersing agent. For such purpose may be employed a soap solution, saponin, nigrosine, or any other material capable of acting as dispersing agent for the carbon black particles.

While it is practical under some conditions to employ carbon black of any commercial degree of fineness, I prefer carbon black made by the channel or impingement process for in employing this' pigment the desirable results above outlined are intensified, that is to say, a more intense color is secured in the product for a minimum amount of pigment and the compressive strength of the resulting concrete is less reduced.

As an example of the result secured, it may be stated that a sample block of uncolored concrete the composition above set forth possesses a compressive strength of approximately 2275 pounds per square inch after setting for 7 days. When this same composition is colored'by the dispersed form in an amount equal to 3% of the cement employed, the compressive strength of the set concrete was reduced to 2245 pounds per square inch, which represents a reduction in strength of less than 2%. The color of the sample, however, in its intensity corresponds subaddition of impalpable carbon black in colloidally stantially to the color secured in the same mixture by the addition to the cement portionof 10% of commercial carbon black not colloidally dispersed and in a sample thus colored the compressive strength is reduced to 1500 pounds per square inch, which represents a reduction in said paste with the ingredients of the concrete,

and subsequently pouring the concrete.

2; In a method of producing a dark colored concrete of relatively high compressive strength,

proximating 3% of the cement content thereof.

3.1namethod of producing an intense permanent black concrete of high compressive strength, the step of adding to the concrete mixture carbon black 'in an amount equal approximately to 3%of thecement content of the mixture, said carbon black being in colloidal suspension with nigrosine as a dispersing agent.

4. An improved dark colored concrete of relatively high compressive strength having distribthe step of adding to the concrete mixture carbon black in colloidal suspension in an amount aputed throughout its mass carbon black, the particles of which are dispersedin colloidal form in the concrete, as produced by the method 01' claim 1. V.

5. An improved dark colored concrete of relatively high compressive strength having distributed throughout its mass carbon black in colloidal form of an amount approximating 3% of the cement content of the concrete, as produced by the method of claim 2.

FRED H. AMON. 

